The present invention is directed to automotive roadwheels and more particularly pertains to a method of reducing the amount of weight that would otherwise need to be added to a wheel during the tire balancing operation.
Proper rotational balance of an automobile""s tires is essential in order to provide a smooth ride, optimize handling characteristics, minimize wear and tear to the vehicle and extend the service life of the tires. A tire is normally balanced after its mounting to a wheel by the attachment of weight to the wheel. The balancing procedure typically comprises the steps of spinning the wheel and tire assembly up to speed, measuring the forces generated by any imbalances, determining the amount of weight and the precise placement of such weight necessary to counteract the measured forces and clipping or adhering weights to the wheel. In order to achieve dynamic balance it is usually necessary for balancing weights to be attached to both the inboard as well as outboard edges of the wheel. The clip-on weights are attached directly to the wheel flanges while the adhesive weights are usually attached to the curb side and brake side of the wheel immediately adjacent to the wheel""s flanges. If the wheel is sufficiently offset, the weight required on the outboard edge of the wheel can sometimes be hidden by attaching it to the wheel just inboard of the wheel""s center element. The assembly is then again spun up to speed to confirm that proper balance has been achieved. Occasionally, the entire balancing procedure must be repeated if a further readjustment is found to be necessary.
The source of an imbalance in a tire and wheel combination is often a combination of imbalances inherent in the tire as well as the wheel. With the trend toward the use of larger and larger wheels and tires for automotive applications, more and more balancing weight often needs to be added in order to achieve an acceptable degree of balance. Moreover, the use of larger diameter wheels in combination with lower profile tires will cause the wheel to be comprise a greater proportion of the total weight of the assembly and therefore, the wheel may be the source of a greater proportion of the total imbalance. The popularity of chrome on wheels further compounds the problem as the chroming process may add significant imbalances to a wheel.
The need to attach balancing weight during the tire balancing operation is somewhat problematic. The weights are typically made of lead which is removed and discarded with each balancing operation. Moreover, the balancing operation itself may cause some waste as a trial and error may be needed in order to achieve an acceptable degree of balance. Not only does the repeated replacement of the weights involve some cost, but the wheel""s protective coating may be damaged in the process and an environmental issue is raised if the disposal or recycling of the removed weights is not properly undertaken. Additionally, the presence of balancing weights on the outboard edge of the wheel is considered rather unsightly by some.
It is therefore highly desirable to minimize the amount of weight that must be added during the tire balancing operation to bring a wheel and tire combination into balance. By reducing the amount of balancing weight that is required, a reduction of waste as well as an amelioration of the environmental concerns can be realized. Additionally, the need to attach less weight to the outboard edge of the wheel is aesthetically advantageous.
The present invention overcomes the shortcomings of previously used methods for achieving balance in a wheel/tire combination. Rather than relying on the tire balancing operation to balance all of the imbalances that may be present in the wheel as well as the tire, the present method provides for permanently achieving a predetermined degree of balance in the wheel before the tire is mounted thereto. Such predetermined degree of balance may involve reducing the wheel""s inherent imbalance to within a range of from zero to an allowable limit, achieving essential a zero imbalance condition or achieving a range about target degree of imbalance. This obviates the need to, in effect, rebalance the wheel with each tire balancing operation and as a result, the amount of balancing weight that is on average needed during the tire balancing operation may be substantially reduced.
More particularly, the present invention provides for determining the imbalances that may be inherent in a wheel before a tire is mounted thereto and applying balancing weight thereto in order to achieve a preselected degree of balance. The balancing weight is preferably permanently attached to the wheel and preferably takes the form of a ballasted adhesive. Such balancing material may be applied to any surface of the wheel so as to avoid interference with any brake or suspension components and so as not to hamper the mounting and seating of the tire. Moreover, the material should be positioned in a relatively protected location so as to avoid dislodgement and should preferably be positioned so as not be visible from the curb side of the wheel. Most preferably, the balancing material is applied to the drop center in the tire side of the wheel wherein the tire will serve to not only hide the material from view but also protect it from the elements and prevent it from becoming dislodged or damaged during normal use.
The balancing process may be fully or partially automated. After determining the magnitude of the imbalance and the location at which the addition of weight would effectively compensate for the imbalance, the amount of adhesive that must be dispensed is calculated. The material is then applied directly to the wheel surface at the predetermined location in any of a variety of configurations. The ballasted adhesive formulation does not sag, sets up in a short period of time and once fully cured, forms an extremely strong and permanent bond with either an unfinished metal surface, a painted surface or a chromed surface of the wheel. Subsequently thereto, a tire is mounted to the wheel and the wheel and tire assembly may then be balanced in the conventional manner.
These and other features and advantages of the present invention will become apparent from the following detailed description of a preferred embodiment which, taken in conjunction with the accompanying drawings, illustrates by way of example the principles of the invention.